What does Allison fault code P0847 mean?

Q: What does Allison fault code P0847 mean?

P0847 indicates: Check Trans / Shift Range Restricted Fix: LOGIC: Transmission Fluid Pressure Switch 3 (C3) Circuit Low. ACTION: Unplug the main transmission case connector. Check continuity of the C3 pressure switch to ground with the engine off (normally open). Trace the internal ribbon harness for chafing or terminal pin corrosion; replace the internal pressure switch manifold (PSM).

Allison Fault Code

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P0847

Check Trans / Shift Range Restricted

System

Pressure Sensing

Symptom

Check Trans / Shift Range Restricted

Diagnosis & fix steps

LOGIC: Transmission Fluid Pressure Switch 3 (C3) Circuit Low. ACTION: Unplug the main transmission case connector. Check continuity of the C3 pressure switch to ground with the engine off (normally open). Trace the internal ribbon harness for chafing or terminal pin corrosion; replace the internal pressure switch manifold (PSM).

Red Seal field insights

Pressure Manifold Contamination: The Allison Pressure Switch Manifold uses metal contact disc diaphragms that sit directly over fluid galleries. Clutch silt accumulates on top of the diaphragms, preventing them from venting cleanly.

Same code keeps coming back?

That's a program problem, not a part problem. Book a 30-minute uptime review with Grant, a Red Seal Heavy Duty Technician.

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Read before you touch anything

This is general reference information, not a repair manual. It is for trained, qualified technicians.
Fault codes, meanings and procedures vary by model, serial number and software version. Confirm the code and the procedure against the manufacturer's service manual before acting.
Follow the OEM service manual, torque specs and your site's safety procedures: lockout/tagout, block raised equipment, relieve hydraulic, fuel and air pressure, and let hot systems cool.
You use this information at your own risk. Adventure Mechanical and AM Fleet Integrity accept no liability for damage, injury, downtime or loss arising from its use.
Not affiliated with or endorsed by any manufacturer. Brand names are used only to identify the equipment a code applies to.

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